In a rotating electrical machine, such as a turbine generator, a gas of hydrogen or the like is used as a cooling medium, for cooling the interior of a main body (for example, Patent Documents 1-5). The cooling media, like a hydrogen gas and others, is sealed on the inside of the rotating electrical machine by a shaft seal device which uses a sealing ring. As to that shaft seal device, oil is supplied to a rear chamber of the sealing ring through a feed oil pipe. The oil moves from that chamber towards the inner circumferential side of the sealing ring. According to the structure described above, the rear face temperature of the sealing ring is lowered in its portion close to an oil supply opening. Because the sealing ring cannot expand (nor deform), an oil film which covers the shaft becomes thinner in the portion close to the oil supply opening, so that temperatures of the oil film rise.
The rise in temperature of the oil film gives rise to cause damage to the sealing ring. In order to curb variations in the temperature, a sealing ring has been fabricated in advance in such a way that its inner diameter may become somewhat large in size, and therefore, the seal oil is consumed excessively there. The specifications of constituent components (a pump, a filter, and the like) of the shaft seal device are designed to cope with this excessive amount of oil. In order to curb the amount of oil which is required to seal the gas, the seal device is suitably designed to have a plurality of oil supply directions which head for the sealing ring. It is to be noted that, because air bubbles are contained in the seal oil, expelling any remaining air from the seal oil is required.